Experimental and theoretical investigation on the hybrid CFRP-ECC flexural strengthening of RC beams with corroded longitudinal reinforcement

This paper reports an experimental and theoretical investigation on the flexural behavior of hybrid engineered cementitious composite (ECC) and carbon fiber reinforced polymer (CFRP) strengthened reinforced concrete (RC) beams with different corrosion levels of longitudinal reinforcement. A certain thickness of damaged concrete cover was removed and replaced by ECC, and CFRP sheets were attached to the soffit of the ECC layer to form the so-called hybrid CFRP-ECC strengthening. Experimental results show that the ECC strengthening could recover the capacity close to that of a virgin beam if the corrosion ratio was less than 10%. Bonding CFRP to ECC in the hybrid CFRP-ECC strengthening prevented CFRP debonding due to the multiple micro-cracking behavior of ECC, thus significantly enhanced the flexural capacity of a beam. The cracking of the remaining upper concrete was better restrained due to the excellent cracking control ability of ECC. In addition to experimental work, theoretical models were proposed to predict the capacity of hybrid CFRP-ECC strengthened beam with corroded flexural steel bars under different failure modes. Model results are found to be in good agreement with test data.